Multi-phase differential synthesis resolver apparatus

ABSTRACT

A novel multi-phase resolver topology and apparatus is provided for measuring a displacement of movement body more precisely and economically. In variable reluctance (VR) resolvers, N coil-poles are placed at N equally spaced positions over one turn of the stator, N being an odd number greater than or equal to 5. Each coil serves both as an excitation and a sensing coil, and all N coils are wound with the same number of turns at an identical electrical polarity. Depending on the installed rotor lobe shape, N sinusoidal or quasi-square waveform displacement signals are sensed on multi-phase resolver, and from which two-phase orthogonal displacement signals are optimally and differentially synthesized. The multi-phase resolver topology and differential synthesis method is also applied to other types of resolvers, such as wound-rotor, inductance, capacitive, and magnetic resolvers.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. patent application Ser.No. 17/170,038, filed Feb. 8, 2021, which claims priority to KoreanPatent Application No. 10-2020-0040974, filed Apr. 3, 2020, thedisclosure of which is incorporated by reference herein in theirentirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The claimed subject matter relates to a resolver apparatus, and moreparticularly, to a novel multi-phase resolver topology, and thedifferential synthesis method, to obtain the precise orthogonal orthree-phase displacement signals of circularly or linearly movingobjects.

2. Description of Related Art

Typical resolvers are electromechanical sensors that measure thedisplacement of moving objects using the principle of electricaltransformer. However, there are many types of resolvers. One commonlyused resolver is a wound-rotor (WR) resolver that comprises of a statorand a rotor, where one primary excitation winding is sinusoidallydistributed on the rotor and two secondary sensing windings are on thestator. The secondary windings are arranged at 90° phase offset eachother so that the two-phase orthogonal displacement signals, sin(θ) andcos(θ), are generated from the secondary windings, as the magnetic fluxfrom the rotor varies sinusoidally. The displacement position (θ) of therotor is calculated by taking the arctangent of the two-phase orthogonaldisplacement signals. Another widely used resolver is a variablereluctance (VR) resolver in which the primary and secondary windings areon the stator as shown in FIG. 1. The reluctance between the stator androtor lobe varies according to the saliencies of the rotor lobe as therotor rotates, even without a brush to drive the excitation winding. Asthe rotor displacement varies, the carrier V sin(ωt) excited on primarycoil (L_(P)) induces a magnetic flux in the stator, and the inducedcurrent flows at sine coil (L_(S)) and cosine coil (L_(C)), sensingtwo-phase orthogonal voltage signals that are amplitude modulated by theexcitation carrier signal sin(ωt). The synchro has three stator windingsinstalled at 120° offsets, while the resolver has two stator windingswith 90° offsets.

When the rotor lobe is stationed at 0°, the induced sine displacementsignal on the sine coil (L_(S)) should be zero. When the rotor lobe isstationed at 90°, the induced cosine displacement signal on the cosinecoil (L_(C)) should also be zero, which implies that the sine and cosinedisplacement signals are to be 100% amplitude modulated by the carrier.To detect the displacement signal precisely, maintaining the propermagnetic flux balance in VR resolver is a primary design factor. Itrequires a sophisticated design and precise manufacturing of thephysical locations of L_(P)-L_(S)-L_(C) as well as their winding turnsand directions of each coil winding. When the load resistor (R_(S)) or(R_(C)) is connected to the secondary coils, the load current flows toeach coil that also causes a magnetic flux distortion at the statorcoils due to an interaction of the consequently induced magnetic flux.

U.S. Pat. No. 10,084,472B1 discloses employing two primary coils and twosecondary coils. Most commercially used VR resolvers have either oneexcitation coil or two excitation coils, and sine and cosine sensingcoils, which are all configured as even-numbered multiple coil-poles inorder to obtain two-phase orthogonal signals that are 100% amplitudemodulated under a state of symmetrically maintaining the magnetic fluxbalance, as illustrated in FIG. 2.

In FIG. 2, the primary driving (excitation) coils (L_(P1), L_(P2), . . ., L_(PN)), sine-signal sensing coils (L_(S1), L_(S2), . . . , L_(SN))and cosine-signal sensing coils (L_(C1), L_(C2), . . . , L_(CN)), arewound separately, and coils of each type are serially connected inalternating coil-winding directions, where N is an even number.Therefore, the magnetic flux (Φ_(Pn), Φ_(Sn), Φ_(Cn)) directions inducedat each pair of coils result in the magnetic flux balance in the stator.

However, the configuration and coil-winding of VR resolvers varieswidely depending on the manufacturers. Chang-Sung Jin, et al. (“Proposalof Improved Winding Method for VR Resolver,” IEEE Trans. Magnetics, vol.51, no. 3, March 2015) discloses that a shift winding method is employedin order to mitigate the complicated coil-winding and increase thesuitability for mass production of VR resolvers. In U.S. Pat. No.8,928,310 B2, some excitation (L_(P)) coils and some sensing coils (sine(L_(S)) and cosine (L_(C))), are partially removed in order tomanufacture more efficiently and economically, and improve the accuracy.In U.S. Pat. No. 6,137,204, each even-numbered coil is wound clock orcounter-clockwise between two coils to maintain the magnetic fluxbalance in three-phase wiring, as illustrated in FIG. 5 of U.S. Pat. No.6,137,204.

As the number of VR resolver winding coil-poles increases to improve theaccuracy, in sensing the precise displacement signals while maintainingthe balanced magnetic flux in the stator, design considerationparameters grow exponentially and its manufacturability becomes morechallenging.

Another main cause of the distortion in the orthogonal signals isimperfect rotor lobe shape. To mitigate this problem, Chengjun Liu etal. (“Analysis of Novel Reluctance Resolver with Asymmetric Teeth on theStator,” Mathematical Problems in Engineering, vol. 2013, Article ID958747, 9 pages) discloses extra compensating coils can be added to theexcitation (L_(P)), sine (L_(S)), and cosine (L_(C)) coils. U.S. Pat.No, 7,030,532 B2 discloses a method of designing the rotor lobe shape totake the high accuracy position information. However, the rotor lobeshape curve is very complex and reducing the tolerance of rotor lobeeccentricity increases its cost.

Moreover, the conventional VR resolver topology makes it difficult toachieve the single (1×) speed resolver due to its physical andstructural constraints, and does not allow for flexibly installing avariety of multi-speed rotor lobes in a given fixed configuration of thestator and coil windings. The position sensing accuracy also abruptlygets worse at the position where the angle of sine signal changes frompositive (+) to negative (−). Another prominent and common problem inthe VR resolver is that the counter-electromotive force also arises atsine (L_(S)) and cosine (L_(C)) coils due to its load current when therotor lobe rotates at high speed, which results in a diminished voltageof the sensed orthogonal signal and a poor detection of positioninformation.

The resolvers have been the only technology of choice for reliablyproviding position feedback under very harsh environments. Most effortsthat have been made to resolvers so far are improving the positionsensing accuracy while reducing the manufacturing difficulties in thecontext of conventional resolver topology, as illustrated in FIG. 2. Thepresent invention seeks a solution in the context of a novel multi-phaseresolver topology and a signal processing technique of its multi-phasesignals.

In International Application Publication No. WO 2020/149489 by thepresent inventor, it is disclosed that N sequentially phase-delayeddisplacement signals over one electrical period can be represented by asystem of linear equations with two unknown variables, namely thetwo-phase orthogonal signals of sine and cosine. Therefore, thetwo-phase orthogonal signals can be mathematically calculated by solvingthe system of linear equations that involves a matrix inversion.Applying the inverse matrix to N phase-delayed displacement signals torecover their two-phase orthogonal signal is analogous to applyingzero-forcing (ZF) linear equalization (or simply “Zero-Force (ZF)Transformation”). Thus, the optimal two-phase orthogonal displacementsignals that are distortion minimized can be synthesized from theimplemented op-amp circuitry having synthesis coefficients calculatedand obtained from the ZF transformation. It also discloses a simple ideafor the resolver and capacitive encoder application, where the sensedN-phase signals are presupposed to be 100% amplitude modulated by thedriving carrier, and the synthesized two-phase orthogonal signals areassumed to be ideally de-modulated.

However, actual resolvers are very sensitive and complex in sensing thedisplacement from the subtle magnetic flux variation. Thus, morecomplicated and sophisticated rotor, stator and coil winding techniquesare required to attain the 100% amplitude modulated and precisedisplacement signals in the conventional resolvers. To mitigate theseobstacles, the present invention discloses a novel and comprehensivemulti-phase resolver design. The multi-phase resolver topology is simplebut very effective in generating N sequentially phase-delayeddisplacement signals that are amplitude modulated (AM) by the carrier ofdriving (or excitation) signal, in which the attained signals areallowed to be either under-modulated or 100% modulated.

SUMMARY OF THE INVENTION

The present invention has been made in view of the aforementionedbackground, and discloses a novel multi-phase resolver topology indetail and its signal processing based on the principle of the ZFtransformation and differential synthesis method.

In one general aspect, there is provided a multi-phase resolverapparatus for measuring a displacement position of a circular bodymovement or a linear body movement, the multi-phase resolver apparatusincluding: a stator including: an N number of coils each wound on apole, N being an odd integer greater than or equal to 5, the pole beingequidistant over a mechanical period or an electrical period of thestator from another pole, and the N number of coils having a sameelectrical polarity; a plurality of winding turns for each coil, whereineach coil includes a same number of winding turns as the N number ofcoils; and a carrier signal source adapted to parallelly excite the Nnumber of coils, wherein each coil is further adapted to perform atleast one of an excitation function and a sensing function; a rotorincluding; a lobe defining at least one electrical period on the statorover one period of the rotor; and an airgap between the stator and thelobe adapted to induce a displacement signal on the coil-poles; and amagnetic flux induced by the carrier signal source and forming aroundeach of the N number of coils, wherein the magnetic flux from othercoil-poles is equally and symmetrically distributed around each of thepoles.

The stator may further include a plurality of phase-delayed displacementsignals sensed as the rotor rotates, wherein each one of thedisplacement signals is sequentially phase-delayed, the displacementsignals are amplitude under-modulated by the carrier signal source andobtained from the N number of coils, and the number of the plurality ofdisplacement signal is the same as the N number of coils over onemechanical turn of the rotor.

Each of the N number of coils may be subdivided into a k number ofcoils, k being an integer greater than or equal to 3, wherein a numberof the lobe is identical to the k number of subdivided coils on thestator, the k number of subdivided coils is positioned at the sameelectrical angle positions with the k rotor lobe periods on the stator,the k number of subdivided coils is serially connected to one another,and the k number of coils generate one of a plurality of phase-delayeddisplacement signals.

Each of the N number of coils may be subdivided into twosub-excitation-sensing coils on the stator which are positionedsymmetrically at a 180° angle apart from one another in a mechanicalangle with an opposite electrical polarity, wherein the twosub-excitation-sensing coils are serially connected such that the twosub-excitation-sensing coils generate one of a plurality ofphase-delayed displacement signals.

The two sub-excitation-sensing coils may be placed at a dual-statorwherein the dual-stator includes a stator-A and a stator-B on a sharedaxis, wherein a first of the two sub-excitation-sensing coils is placedon the stator-A whereas a second of the two sub-excitation-sensing coilsis placed on the stator-B, wherein the two sub-excitation-sensing coilsare placed at a same electrical angle position and with an oppositeelectrical polarity, wherein the two sub-excitation-sensing-coils areserially connected; and a magnetic flux path A of the stator-A and amagnetic flux path B of the stator-B may be independently formed, andeach of the magnetic flux path A and the magnetic flux path B may bebalanced such that the displacement signal is free of common mode noiseinduced by a directional external magnetic flux toward the multi-phaseresolver apparatus.

Each of the N number of coils may include a primary coil and a secondarycoil, wherein the primary coils are excitation-coils, wherein each oneof the primary coils has a same number of winding turns with anidentical electrical polarity as the other primary coils, wherein thesecondary coils are sensing-coils, wherein each one of the secondarycoils has a same number of winding turns with an identical electricalpolarity as the other secondary coils, and wherein an electric path ofthe primary coils and an electric path of the secondary coils areisolated such that a Galvanic isolation is achieved.

The multi-phase resolver apparatus may have a speed of k number, whereina rotor lobe has a plurality of saliencies, wherein the number ofsaliencies is k, wherein the k number of saliencies produce k electricalperiods through one mechanical turn of the rotor, k being a numberselected from 1 to N minus 1 except a non-trivial divisor of N andany-multiple of any non-trivial divisor of N, wherein the rotor lobeexpands an electrical angle to k times 360° per one mechanical turn andhaving a speed of k number of electrical periods per one mechanical turnof the rotor such that the N number of sequentially phase-delayeddisplacement signals and carrier modulated displacement signals areobtained from the N coil-poles.

The multi-phase resolver apparatus has a speed of k number, wherein k isan integer greater than or equal to 15, wherein a rotor has a pluralityof teeth, wherein the number of rotor teeth is k, wherein each coil-poleincludes a number of teeth between two teeth and ten teeth, wherein aperiod of each tooth on the rotor defines one electrical period of 360°,wherein the teeth on each coil-pole are constructed such as its teethperiod is delayed successively by an inverse of its Nth number againstthe rotor teeth through the N coil-poles, and wherein with a speed of knumber of electrical periods per one mechanical turn of the rotor suchthat the N number of sequentially phase-delayed displacement signals andcarrier modulated displacement signals are obtained from the Ncoil-poles.

The rotor lobe may further includes a rotor lobe for a quasi-squarewaveform signal generation wherein a circumference of the rotor lobe isdivided into an arc shape section of a constant airgap and a slope shapesection of a linearly varying airgap between the stator and rotor lobe,wherein the arc shape section has two saliencies that are symmetricallylocated with different radii such as one is larger than the other, whilethe slope shape section has two saliencies that are symmetricallylocated with the slope, but with opposite direction, and wherein as therotor lobe being displaced, the arc shaped section generates one of ahigher level signal or a lower level signal upon the two differentradii, whereas the slope shaped section generates either a rising edgeor falling edge signal of the quasi-square waveform signal.

The stator may be non-contiguously separated into a number ofstator-bodies wherein the number of stator-bodies is the same as the Nnumber of coil-poles, wherein the number of stator-bodies beingphysically separated and evenly placed at a same electrical positionbefore a separation, wherein each of the coil-poles is placed at each ofthe stator-bodies, and wherein the stator-body is structured such thatit can attain an inductance deemed effective between the stator-body andthe rotor lobe, wherein when the rotor is displaced, the inductancevaries between the stator-bodies and the rotor lobe and N sequentiallyphase-delayed and amplitude modulated displacement signals are sensed.

In another general aspect, there is provided a multi-phase capacitiveresolver apparatus for measuring a displacement of a circular movementbody, the multi-phase capacitive resolver apparatus including: a statorincluding: an N number of metal plates placed at N equally dividedpositions over one mechanical or an electrical period of the stator,wherein the N number of metal plates establishes an N number of statorelectrodes, N being an odd number greater than or equal to 5; a rotorincluding: a rotatable plate having at least one lobe, wherein therotatable plate establishes a rotor electrode, wherein the rotorelectrode is installed in parallel to the N number of stator electrodeswith an airgap, wherein the N number of stator electrodes react as an Nnumber of capacitive elements against the rotor electrode when the rotorrotates, wherein the N number of capacitive elements are excited by adriving carrier signal, wherein capacitive variations are caused betweenthe N number stator electrodes and the rotor electrode as the rotorrotates, wherein a displacement signal having at least one electricalperiod is induced on each of the N number of stator electrodes per onemechanical turn, wherein the induced displacement signal is amplitudemodulated by the driving carrier signal and is sequentiallyphase-delayed.

In a further general aspect, there is provided a multi-phase wound-rotor(WR) resolver apparatus for measuring a displacement position of acircular movement body, the multi-phase WR resolver apparatus including:a stator including: an N number of coil-poles placed at N equallydivided positions over a mechanical or an electrical period of thestator, N being an odd number greater than or equal to 5, wherein the Ncoils have an identical electrical polarity, and are wound with an equalnumber of winding turns, and the N number of coils sense a displacementof the rotor; and a wound-rotor, wherein a coil is wound with asinusoidally distributed winding, a driving signal carrier is applied tothe coil wound on the wound-rotor, and one or more periods of sinusoidalelectrical signals are induced on each of the N number of coils on thestator per one turn of the wound-rotor such that N sequentiallyphase-delayed and amplitude modulated displacement signals are sensedfrom the N number of coils on the stator.

Each of the N number of coils may be subdivided into two sensing-coilson the stator, wherein the two sensing-coils are located at 180°difference in mechanical or electrical angle on the stator, wherein thetwo sensing-coils have an opposite electrical polarity, and are seriallyconnected such that the N number of sequentially phase-delayed andamplitude modulated displacement signals are obtained from N sets of twosubdivided sensing coils.

The two sensing-coils may be placed at a dual stator on a shared axis,wherein the dual-stator includes a stator-A and a stator-B on a sharedaxis, wherein the two sensing-coils are separately placed on thestator-A and the stator-B at a same electrical angle position, with anopposite electrical polarity, and are serially connected, wherein aphase-delayed displacement signal, free of a common mode noise inducedfrom a directional external magnetic flux toward the resolver, isattained through the two sensing-coils on the dual stator and whereinthe N number of sequentially phase-delayed and amplitude modulateddisplacement signals are obtained from N sets of the two sensing coilson the dual stator.

In a still further general aspect, there is provided a differentialsynthesis apparatus adapted to sense a plurality of amplitude modulatedphase-delayed displacement signals and outputs amplitude modulatedtwo-phase orthogonal displacement signals, wherein the differentialsynthesis apparatus utilizes sine synthesis coefficients and cosinesynthesis coefficients being selectable from a Zero-Forcetransformation, and wherein the differential synthesis apparatus removesat least one of a common mode noise induced by an external disturbanceflux and an unmodulated carrier signal component.

The differential synthesis apparatus may be realized by an electricalcircuitry and include: a differential sine synthesis module implementedin an OP-amp circuitry, wherein the OP-amp circuitry includes: an Nnumber of sensing resistors, each connected to a primary differentialOP-amp, wherein the N number of sensing resistors are sorted into agroup of negative-sign sensing resistors for the negative sine synthesiscoefficients and a group of positive-sign sensing resistors for thepositive sine synthesis coefficients; and the primary differentialOP-amp, wherein the negative-sign sensing resistors are connected to anegative (−) input port of the primary OP-amp, and the positive-signsensing resistors are connected to a positive (+) input port of theprimary OP-amp, wherein the negative input port and an output of theprimary OP-amp is connected by a primary feedback gain register, whilethe positive input port and the reference level (ground) is connected bya primary match register such that each resistor value is determined bya ratio between the value of the primary feedback gain resistor and thevalue of corresponding sine synthesis coefficient under a specificcondition that the value of the primary feedback gain register is equalto that of the primary match register, wherein an un-modulated carriersignal component and common mode noise in a signal, if any included, isremoved through the primary differential OP-amp as a common mode noiserejection; and a differential cosine synthesis module implemented in anOP-amp circuitry, wherein the OP-amp circuitry includes: an N number ofsensing resistors, each connected to a secondary differential OP-amp,wherein the N number of sensing resistors are sorted into a group ofnegative-sign sensing resistors for the negative cosine synthesiscoefficients and a group of positive-sign sensing resistors for thepositive cosine synthesis coefficients; and the secondary differentialOP-amp, wherein the negative-sign sensing resistors are connected to thenegative (−) input port of the secondary OP-amp, and the positive-signsensing resistors are connected to the positive (+) input port of thesecondary OP-amp, wherein the negative input port and the output of thesecondary OP-amp is connected by a secondary feedback gain register,while the positive input port and the reference level (ground) isconnected by a secondary match register such that each resistor value isdetermined by the ratio between the value of the secondary feedback gainresistor and the value of a corresponding cosine synthesis coefficientunder a specific condition that the value of the secondary feedback gainregister is equal to that of the secondary match register, wherein anun-modulated carrier signal component and common mode noise in a signal,if any included, is removed through the secondary differential OP-amp asa common mode noise rejection.

The differential synthesis apparatus may further include: a statorincluding an N number of magnetic sensors, wherein N being an oddinteger greater than or equal to 5, wherein the magnetic sensors beingequidistant over a mechanical period or an electrical period of thestator from another magnetic sensor; and a rotor including a pluralityof magnets wherein each turn of the rotor generates at least oneelectrical period on the stator, wherein the stator outputs a pluralityof phase-delayed displacement signals as the rotor rotates, wherein eachone of the displacement signals is sequentially phase-delayed, wherein aplurality of displacement signals are obtained from the N number ofmagnetic sensors, and wherein the number of the plurality ofdisplacement signal is the same as the N number of magnetic sensors overone mechanical turn of the rotor.

The differential synthesis apparatus may further include: a moverincluding an N number of magnetic sensors, wherein N being an oddinteger greater than or equal to 5, wherein the magnetic sensors beingequidistant over a mechanical period or an electrical period of themover from another magnetic sensor; and a stator including a pluralityof magnets wherein a displacement of the mover generates at least oneelectrical period on the stator, wherein the mover outputs a pluralityof phase-delayed displacement signals as the mover moves, wherein eachone of the displacement signals is sequentially phase-delayed, wherein aplurality of displacement signals are obtained from the N number ofmagnetic sensors, and wherein the number of the plurality ofdisplacement signals is the same as the N number of magnetic sensorsover one mechanical turn of the mover.

The differential synthesis apparatus may further include: aphase-sensitive demodulator to demodulate the amplitude modulatedtwo-phase orthogonal displacement signals, and converts them intotwo-phase orthogonal displacement signals without the carrier; and aninterpolator to determine an absolute position or incremental positionof a rotor.

The differential synthesis apparatus may further include: an A/Dconverter adapted to convert an orthogonal displacement signal into adigital signal and outputs a digital orthogonal displacement signal; aHilbert Transformer adapted to shift the carrier phase of the digitalorthogonal displacement signal by 90°; an adder adapted to add theoutput signal of the Hilbert Transformer and the original signal ofwhich carrier phase is not shifted and outputs an complex signal; and anabsolute calculator adapted to calculate an absolute value of thecomplex signal and outputs a carrier-removed orthogonal displacementsignal.

The differential synthesis apparatus may output amplitude modulatedthree-phase displacement signals, wherein the amplitude modulatedthree-phase displacement signals have phases of 0°, 120°, and 240°,wherein the differential synthesis apparatus utilizes three sets ofsynthesis coefficients being selectable from a Zero-Forcetransformation.

One or more of the above-disclosed embodiments in addition to certainalternatives are provided in further detail below with reference to theattached figures. The claimed subject matter is not, however, limited toany particular embodiment disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the claimed subject matter are understood by referring tothe figures in the attached drawings, as provided below.

FIG. 1 illustrates the conventional variable reluctance (VR) resolverarchitecture and its operational principle.

FIG. 2 illustrates an exemplary coil-winding of the conventional VRresolver.

FIG. 3A illustrates an exemplary coil-winding of N coil-poles,single-wound N-phase VR resolver according to the present invention.

FIG. 3B illustrates an exemplary topology of 5 coil-poles, single-wound5-phase VR resolver according to the present invention.

FIG. 3C illustrates an exemplary topology of 11 coil-poles, single-wound11-phase VR resolver according to the present invention.

FIG. 4 shows an exemplary driving (excitation) signal and 5-phaseamplitude modulated displacement signals sensed on 5-phase VR resolverof FIG. 3B.

FIG. 5 shows an exemplary block diagram of multi-phase VR resolveraccording to the present invention.

FIG. 6 shows an exemplary input and output signals of differentialsynthesis module (200) for 5-phase resolver according to the presentinvention.

FIG. 7 shows an exemplary detailed schematic of differential synthesismodule (200) for N-phase resolver according to the present invention.

FIG. 8 shows an exemplary detailed schematic of differential synthesismodule (200) for 5-phase resolver according to the present invention.

FIG. 9A illustrates an exemplary coil-winding of balance-wired N-phaseVR resolver according to the present invention.

FIG. 9B illustrates an exemplary topology of balance-wired 5-phase VRresolver according to the present invention.

FIG. 9C illustrates an exemplary coil-winding of balance-wiredmulti-phase VR resolver having dual stators according to the presentinvention.

FIG. 9D illustrates an exemplary coil-winding of double-wound N-phase VRresolver according to the present invention.

FIG. 9E illustrates an exemplary topology of 5-phase variable inductanceresolver according to the present invention.

FIG. 9F plots exemplary inductance variations of the inductive resolverof 5-phase variable inductance resolver of FIG. 9E.

FIG. 9G illustrates an exemplary PCB type stator for the 5-phasevariable inductance resolver according to the present invention.

FIG. 9H illustrates an exemplary 1× rotor lobe installed in the PCB-type5-phase variable inductance resolver according to the present invention.

FIG. 9I illustrates an exemplary functional diagram of the 5-phasemagnetic resolver according to the present invention.

FIG. 10A illustrates an exemplary topology of 11-phase VR resolverinstalled with 1× quasi-square waveform rotor lobe according to thepresent invention.

FIG. 10B illustrates an expected envelope of quasi-square waveformdisplacement signal by the quasi-square waveform rotor lobe according tothe present invention.

FIG. 10C illustrates an exemplary amplitude modulated quasi-squarewaveform displacement signal by the quasi-square waveform rotor lobeaccording to the present invention.

FIG. 10D illustrates an exemplary sine orthogonal signal (V sin), outputof differential synthesis module (200A) when quasi-square waveform rotorlobe is installed.

FIG. 10E shows an exemplary cosine orthogonal signal (V cos), output ofdifferential synthesis module (200B) when quasi-square waveform rotorlobe is installed.

FIG. 10F shows a Lissajous graph of two-phase orthogonal displacementsignals when quasi-square-waveform rotor lobe is installed.

FIG. 10G shows a Lissajous graph of two-phase orthogonal displacementsignals after removing the carrier signal component when quasi-squarewaveform rotor lobe is installed.

FIG. 10H shows a Lissajous graph of two-phase orthogonal displacementsignals directly obtained from the conventional VR resolvers whenquasi-square waveform rotor lobe is installed.

FIGS. 11A to 11J illustrates a topology of multi-speed 11-phase VRresolver when 1×˜10× sinusoidal-waveform rotor lobe, respectively, isinstalled according to the present invention.

FIG. 11K illustrates an exemplary topology of k× speed 5-phase VRresolver, where the stator has 5 stator teeth, each successively ⅕thteeth shifted, and k rotor teeth (102 a) lobe is installed according tothe present invention.

FIG. 12A draws an exemplary block diagram of digital demodulation of theamplitude modulated signal by Hilbert Transform according to the presentinvention.

FIG. 12B draws an exemplary block diagram of recovering the carriersignal from N-phase amplitude modulated displacement signals sensed onN-phase resolver according to the present invention.

FIG. 12C draws an exemplary block diagram of synchro transmitter,generating three-phase displacement signals from N-phase resolveraccording to the present invention.

FIG. 12D draws an exemplary topology of 5-phase wound-rotor resolveraccording to the present invention.

FIG. 12E draws an exemplary topology of 5-phase capacitive resolveraccording to the present invention.

FIG. 12F draws a functional and differential synthesis circuitry diagramof the 5-phase capacitive resolver according to the present invention.

FIG. 13A is a picture of fabricated stator coil-windings of single-wound9-phase VR resolver according to the present invention.

FIG. 13B is a picture of fabricated stator coil-windings ofbalance-wired 9-phase VR resolver according to the present invention.

FIG. 14A is a picture of fabricated rotor lobe of 1× quasi-squarewaveform according to the present invention.

FIG. 14B is a picture of fabricated rotor lobe of 4× sinusoidal-waveformaccording to the present invention.

FIG. 15A is a picture of assembled single-wound 9-phase VR resolveraccording to the present invention.

FIG. 15B is a picture of assembled balance-wired 9-phase VR resolveraccording to the present invention.

FIG. 16A shows an exemplary captured picture on oscilloscope of adisplacement signal sensed on the single-wound 9-phase VR resolver when1× quasi-square waveform rotor lobe is installed.

FIG. 16B shows an exemplary captured picture on oscilloscope of aLissajous graph for two-phase orthogonal displacement signals obtainedfrom single-wound 9-phase VR resolver when 1× quasi-square waveformrotor lobe is installed.

FIG. 17A shows an exemplary captured picture on oscilloscope of adisplacement signal sensed on the single-wound 9-phase VR resolver when4× sinusoidal-waveform rotor lobe is installed.

FIG. 17B shows an exemplary captured picture on oscilloscope of aLissajous graph for two-phase orthogonal displacement signals obtainedfrom single-wound 9-phase VR resolver when 4× sinusoidal-waveform rotorlobe is installed.

FIG. 18A shows an exemplary captured picture on oscilloscope of adisplacement signal sensed on the balance-wired 9-phase VR resolver when4× sinusoidal-waveform rotor lobe is installed.

FIG. 18B shows an exemplary captured picture on oscilloscope of aLissajous graph for two-phase orthogonal displacement signals obtainedfrom balance-wired 9-phase VR resolver when 4× sinusoidal-waveform rotorlobe is installed.

Features, elements, and aspects that are referenced by the same numeralsin different figures represent the same, equivalent, or similarfeatures, elements, or aspects, in accordance with one or moreembodiments.

DETAILED DESCRIPTION OF THE INVENTION

In the following, numerous specific details are set forth to provide athorough description of various embodiments of the claimed subjectmatter. Certain embodiments may be practiced without these specificdetails or with some variations in detail. In some instances, certainfeatures are described in less detail so as not to obscure other aspectsof the disclosed embodiments. The level of detail associated with eachof the elements or features should not be construed to qualify thenovelty or importance of one feature over the others.

To facilitate understanding the present invention, a following glossaryof terms is provided. The glossary is intended to provide the readerwith a general understanding of various terms as they are used in thespecification and claims, and is not intended to limit the scope ofthese terms.

Glossary of Terms

Amplitude modulated (AM) signal—The term “amplitude modulated (AM)signal” as used herein in this specification, is defined as a signalthat is amplitude modulated by the carrier of a high frequency driving(or excitation) signal. An AM signal can be either under-modulated(modulation index is less than 1.0) or 100% modulated (modulation indexis 1.0).

Balance-wired—The term “balance-wired” as used herein in thisspecification, is defined as a configuration of coil-poles such that atleast two sensing coils or excitation-sensing coils are wound ondifferent poles to maintain flux balance between the coil-poles and tosense a rotor displacement signal at a certain phase.

Coil-pole—The term “coil-pole” as used herein in this specification, isdefined as a pole on which one or multiple coils are wound.

Differential synthesis—The term “differential synthesis” as used hereinin this specification, is defined as a method and an apparatus thatsynthesizes two-phase orthogonal or three-phase displacement signalsfrom sequentially phase delayed displacement signals sensed on themulti-phase resolver by performing the Zero-Force transformation in adifferential way.

Double-wound—The term “double-wound” as used herein in thisspecification, is defined as a configuration of coil-poles such that aprimary coil for excitation and a secondary coil for sensing are woundon a same pole or other separate pole to achieve Galvanic isolation andto sense a rotor displacement signal at a certain phase.

Excitation-sensing coil—The term “excitation-sensing coil” as usedherein in this specification, is defined as a coil wound on a pole,which performs both an excitation function on a driving carrier signaland a sensing function on the rotor displacement.

Multi-phase—The term “multi-phase” as used herein in this specification,is defined as the number of phases of displacement signals, sensed fromthe resolver body, which is greater than or equal to 5. In conventionalresolvers, typically two-phase or three-phase displacement signals aresensed.

N-phase—The term “N-phase” as used herein in this specification, isdefined as an N number of phases that are equally divided over onemechanical or electrical period of 360°. In N-phase of multi-phaseresolver, N phase-delayed displacement signals are sensed over onemechanical turn or electrical period of the rotor displacement.

Pole—The term “pole” as used herein in this specification, is defined asa protruding shape like tooth on the stator, on which one or multiplecoils may or may not be wound.

Primary coil (or winding)—The term “primary coil (or winding)” as usedherein in this specification, is defined as a coil wound on a pole thatperforms an excitation function on a driving carrier signal.

Resolver—The term “resolver” as used herein in this specification, isdefined as an apparatus adapted to measure the position of a movingobject. The resolver comprises at least one stator and at least onerotor.

Lobe—The term “lobe” as used herein in this specification, is defined asa part of rotor, of which saliencies (or teeth) produce one or multipleelectrical periods over one mechanical turn of the rotor.

Secondary coil (or winding)—The term “secondary coil (or winding)” asused herein in this specification, is defined as a coil wound on a polethat performs a sensing function on the rotor displacement.

Single-wound—The term “single-wound” as used herein in thisspecification, is defined as a configuration of coil-poles such thatsingle excitation-sensing coil doing excitation and sensingsimultaneously is wound on a pole to sense a rotor displacement signalat a certain phase.

Synthesis coefficients—The term “synthesis coefficients” as used hereinin this specification, is defined as a set of numbers that is selectedfrom the ZF transformation and is utilized in the differentialsynthesis. The method of selecting synthesis coefficients is disclosedin International Application Publication No. WO 2020/149489.

Zero-Force (ZF) transformation—The term “Zero-Force (ZF) transformation”as used herein in this specification, is defined as a 1^(st) orderlinear transformation in mathematics or electrical engineering such thatan N number of sequentially phase delayed signals are transformed intotwo-phase orthogonal signals or three-phase displacement signals inzero-forcing criterion. The method and apparatus of the ZFtransformation is disclosed in International Application Publication No.WO 2020/149489.

The present invention disclosure provides a remarkably simplified andflexible multi-phase resolver topology and its differential signalprocessing method that significantly reduces the manufacturing cost andquality control requirements, while improving the position detectionaccuracy.

The embodiment of the invention mainly describes VR resolvers because oftheir simplicity and cost effectiveness but it can also be fully appliedto WR resolvers or other types of resolvers that share the basicprinciples.

The multi-phase resolver apparatus includes largely two parts; one is amulti-phase resolver body that relates to the architecture of theresolver coil windings, the stator and the rotor; the other is a signalprocessing unit that includes exciting the carrier signal, sensing thedisplacement signal from the multi-phase resolver body, differentialsynthesizing on synthesis coefficients, removing the common-mode signalssuch as un-modulated carrier, and recovering the carrier modulateddisplacement position signal such as single-phase, two-phase orthogonal,or three-phase synchro compatible signals, and resolver-to-digitalconversion.

Let N be a phase-division number that divides one electrical ormechanical period of 360° equally into N positions, then the anglebetween two adjacent positions, which is referred to as “phase-divisionangle” (or simply “phase”) becomes 360°/N, where N is an odd numbergreater than or equal to 5 in the present invention, unless otherwisenoted. Considering the size of the stator practically used in theindustries, however, N would be around 5 to 99.

The multi-phase resolver has a new topology compared with that ofconventional resolvers. An exemplary schematic circuit diagram of ageneric single-wound N-phase VR resolver according to the presentinvention is illustrated in FIG. 3A, where N coils, L₁, L₂, . . . ,L_(N), are wound on the poles of the stator and connected in parallel,and N is an odd number greater than or equal to 5. Physically, N coilsare allocated at evenly spaced positions, more exactly, at theelectrical positions on N equally divided over one mechanical orelectrical period of the stator, where the electrical period is formedby the rotor lobe. In FIG. 3A, each coil has the function ofsimultaneously excitation (driving) and sensing, whereas generally threetypes (excitation, sine-signal sensing, and cosine-signal sensing) ofcoils are wound on each pole in conventional VR resolvers as shown inFIG. 2. In the generic single-wound multi-phase VR resolver, all coilsare wound at the same electrical polarity with an identical number ofturns.

Compared with the conventional VR resolver, the major distinct featuresin single-wound multi-phase VR resolver are as follows: (1) multi-phaseVR resolver is configured to have an odd-numbered N coil-poles, whichare connected and excited in parallel, whereas generally an even numberof coil-poles are configured in conventional VR resolvers, which areconnected serially; (2) single coil is wound on each pole for thepurpose of exciting and sensing the signal, whereas in conventional VRresolvers, generally three types of coils are overlappingly wound oneach pole for excitation, sine signal sensing, and cosine signalsensing; (3) all coils have the same number of turns and identicalelectrical polarity, whereas in conventional VR resolvers, generally thenumber of coil turns varies from pole to pole and depends on the signaltype of coils with a varying winding direction; (4) AM under-modulationis allowed, whereas 100% modulation is necessary in conventional VRresolvers; (5) as the rotor rotates, successively N phase-delayedsinusoidal displacement signals are sensed on N coils, whereas inconventional VR resolvers, two-phase orthogonal displacement signals aredirectly sensed through multiple sine and cosine sensing coils; and (6)differential signal processing is applied to N phase-delayed sinusoidaldisplacement signals to produce the two-phase orthogonal displacementsignals.

Feature (1) of the multi-phase resolver topology enables to sense adisplacement signal at each coil-pole independently without beingdisturbed by the carrier magnetic flux interferences from othercoil-poles. Features (2) and (3) of the multi-phase VR resolversignificantly reduce the complicated task of fabricating three layers ofcoil windings in conventional VR resolver manufacturing, as well asincrease the reliability of the resolver as it is possible for the threetypes of coils to short circuit due to insulation damage in the slendercoil wire. Feature (4) significantly relaxes the tight requirements ofcoil winding and configuration in multi-phase resolvers, which arecritical to achieve 100% amplitude modulated signals in conventionalresolvers. Feature (5) describes that the sum of all N phase-delayeddisplacement signals sensed on the multi-phase resolver becomes zero asthe sum of all N equally phase-delayed periodic signals ismathematically zero in one period. In other words, the stator is in abalanced magnetic flux state at any position. This balanced magneticflux state together with feature (1)'s topology obviates the need toperform complicated tasks to maintain the magnetic flux balance requiredin conventional VR resolvers. Feature (5) also offers a means ofmonitoring the integrity of a manufactured multi-phase VR resolver asthe sum of all carrier signal components in N phase-delayed displacementsignals is assumed to be constant under the ideal condition. The signalprocessing described in Feature (6) of the multi-phase VR resolverminimizes the noise and distortion induced in the sensed signals.

FIG. 3B illustrates a topology of generic single-wound 5 coil-poles,N=5, so 5-phase VR resolver according to the present invention; 5excitation-sensing coils, L₁, L₂, L₃, L₄, and L₅, are located at 0°,72°, 144°, 216°, and 288° phase-angle positions, respectively, aroundthe stator (101) by the phase-division angle 360°/5=72°. Thus, as therotor rotates, sequentially 5-phase sinusoidal displacement signals aregenerated on the five coils. The same topology can be applied to amulti-phase WR resolver, where odd-numbered N sensing coils are equallyspaced on the stator.

A driving carrier signal excites in parallel the excitation-sensingcoils, L1, L2, . . . , Ln. When the rotor starts to rotate, the magneticfield is established throughout the whole stator and on theexcitation-sensing coils according to the rotated position of the rotorthrough the air-gap permeance formed by the particular shape of rotor(102) lobe. A distinctive characteristic of multi-phase VR resolvertopology is that the carrier induced magnetic flux distribution aroundthe stator is optimally balanced in sensing the displacement signal ofthe rotor by the configuration of evenly spaced layout of odd-numbered Ncoil-poles with a proper carrier excitation. From the perspective of acertain coil-pole position, the flux weighed on the coil-pole on theright side is balanced with the flux weighed on the coil-pole on theleft side as they are symmetrically located with equal distance but withthe opposite magnetic flux directions. Therefore, eachexcitation-sensing coil is able to sense a clean phase-delayeddisplacement signal independently without interference from the othercoil-poles.

When an even number of coil-poles are placed at evenly divided positionson the stator, the carrier magnetic flux induced to a certainexcitation-sensing coil interferes with other coil-poles as the fluxbalance weighed on that coil-pole is unbalanced due to the brokensymmetricity from the resultant odd number of coil-poles around thecoil-pole.

When the driving carrier excitation signal, V_(S), is excited toexcitation-sensing coils L1, L2, . . . , Ln, a successively phase-angledelayed current flows through each coil and consequently, the magneticflux Φ₁, Φ₂, . . . , Φ_(N), is formed as the rotor rotates. A signalthat is amplitude modulated by the carrier is sensed at eachexcitation-sensing coil, L1, L2, . . . , Ln, by the connecting sensingresister, R₁, R₂, . . . , R_(N), to each coil, respectively.

The total sum of currents caused by displacement signals flowing throughall excitation-sensing coils must be zero since the sum of all N equallyphase-delayed periodic signals is zero in one period mathematically.Therefore, the sum of all magnetic flux in the stator must be zeromathematically as in EQ. (1).

Φ₁+Φ₂+ . . . +Φ_(N)=0   EQ. (1)

EQ. (1) implies that the stator is physically in a balanced magneticflux state when the rotor lobe is at any stationary position.

When the rotor starts to rotate, the sensed signal, V₁, V₂, . . . ,V_(N), is expressed as follows with carrier frequency ω:

$\begin{matrix}\begin{matrix}{V_{1} = {{K\left( {1 + {m \times {\sin\left( {\theta - \theta_{1}} \right)}}} \right)} \times {\sin\left( {\omega\; t} \right)}}} \\{V_{2} = {{K\left( {1 + {m \times {\sin\left( {\theta - \theta_{2}} \right)}}} \right)} \times {\sin\left( {\omega\; t} \right)}}} \\\vdots \\{V_{N} = {{K\left( {1 + {m \times {\sin\left( {\theta - \theta_{N}} \right)}}} \right)} \times {\sin\left( {\omega\; t} \right)}}}\end{matrix} & {{EQ}.\mspace{14mu}(2)}\end{matrix}$

In EQ. (2), θ_(n) is an electrical angle at which L_(n)excitation-sensing coil is located,

$\theta_{n} = {\frac{360}{N} \times \left( {n - 1} \right)}$

for n=1, 2, . . . , N. K is a VR resolver transfer ratio and mrepresents a modulation ratio. The VR resolver transfer ratio (K) isdetermined from several factors such as the number of turns of coil, thelength of magnetic circuit, construction structure, resolver materialsand the airgap length between the rotor lobe and the stator.

EQ. (2) states that N successively phase delayed (or simply “N-phase”)displacement signals are sensed without any interference from the othercoil-poles.

In FIGS. 3B and 3C, a topology of 5 coil-poles (N=5) and 11 coil-poles(N=11) of generic single-wound VR resolver is drawn, where thephase-division angle is 360°/5=72° and 360°/11=32.73°, respectively.

For the 5 coil-poles, 5-phase VR resolver in FIG. 3B, the waveforms ofexcitation signal, V_(S)=V sin(ωt), and amplitude modulated sensedsignals, V₁, V₂, V₃, V₄, and V₅, are shown in FIG. 4, respectively. Itis seen that the envelope of V₁, V₂, V₃, V₄, and V₅ signal is asequentially 72° phase-delayed displacement signal.

The amplitude modulated sensed multi-phase signals are usuallyunder-modulated for the single-wound windings. To obtain two-phaseorthogonal displacement signals, which are amplitude modulated by thecarrier and are compatible with conventional resolvers, a proper signalprocessing is required.

FIG. 5 illustrates an exemplary block diagram of multi-phase VR resolveraccording to the present invention. It mainly consists of the resolverbody (100) and the differential synthesis module (200). The excitationcarrier signal V_(S) generator (302) can be included in a commerciallyavailable R/D converter.

In implementing the circuitry of removing the component of un-modulatedcarrier signal while processing the differential synthesis, the ordinarydifferential OP-amp circuits with odd number of input cannot be easilyapplied as the sensed signals are asymmetry in number and phase. Byexploiting the inherent characteristics of ZF transformation when N isan odd number, however, the invention presents a differential synthesismodule realized by the ingenious differential OP-amp circuitry incanceling the carrier signal component through the common mode signalrejection. The sensing gain resistors that correspond to the synthesiscoefficients are also conveniently determined.

In response to the carrier signal V_(S) from driving (excitation) signalsource, the resolver body (100) generates sequentially N phase-delayeddisplacement signals in EQ. (2). The differential synthesis module(200), which comprises a sine synthesis module (200A) and a cosinesynthesis module (200B), processes the N-phase signals and produces theamplitude modulated two-phase orthogonal displacement signals, V_(sin)and V_(cos).

In FIG. 6, 5-phase amplitude under-modulated signals, V₁, V₂, V₃, V₄,and V₅, are illustrated in detail. The amplitude under-modulated signalcan be divided into two signals: one is a modulated signal that containsa displacement information sin(θ−Δθ), and the other is an un-modulatedcarrier signal sin(ωt). The un-modulated carrier signal sin(ωt), whichis common to all signals, can be removed by a differentialamplification. The sin(θ−Δθ) signals contain the information of rotordisplacement position.

When sine addition formula, sin(θ−Δθ)=sin(θ)*cos(Δθ)−cos(θ)*sin(Δθ), isapplied, the amplitude modulated 5-phase displacement signals can beexpressed as follows after ignoring the carrier signal:

V ₁=

(θ−Δθ₁)=

(θ)*cos(Δθ₁)−cos(θ)*

(Δθ₁)

V ₂=

(θ−Δθ₂)=

(θ)*cos(Δθ₂)−cos(θ)*

(Δθ₂)

V ₃=

(θ−Δθ₃)=

(θ)*cos(Δθ₃)−cos(θ)*

(Δθ₃)

V ₄=

(θ−Δθ₄)=

(θ)*cos(Δθ₄)−cos(θ)*

(Δθ₄)

V ₅=

(θ−Δθ₅)=

(θ)*cos(Δθ₅)−cos(θ)*

(Δθ₅)

The above 1^(st) degree system of linear equations with two variables,sin(θ)=V_(sin) and cos(θ)=V_(cos), can be solved by finding the inversetransformation of the linear system matrix. In other words, sin(θ) andcos(θ) is synthesized from V₁, V₂, V₃, V₄, and V₅ in differential way toremove the un-modulated carrier signal component.

Let the solution of the above equations be (a1, a2, a3, a4, a5), sinesynthesis coefficients for the synthesis of sin(θ) variable, and (b1,b2, b3, b4, b5), cosine synthesis coefficients for the synthesis ofcos(θ) variable, then V_(sin) and V_(cos) is the linear combination ofthe 5-phase displacement signals as follows:

V _(z,24) =(a1*V ₁)+(a2*V ₂)+(a3*V ₃)+(a4*V ₄)+(a5*V ₅)

V _(cos)=(b1*V ₁)+(b2*V ₂)+(b3*V ₃)+(b4*V ₄)+(b5* V ₅)

The coefficient in the above linear equation has its normalized valuebetween −1˜1, and using the property of ZF transformation, the equationcan be suitably implemented by a differential operational amplifier(OP-amp) circuitry. For both V sin and V cos calculations, signalshaving plus coefficient (positive sign) are input to the positive Op-ampinput port and signals having minus coefficient (negative sign) areinput to the negative Op-amp input port. A sensing resistor value foreach signal that represents the absolute value of each correspondingsynthesis coefficient becomes the gain of the signal.

The two-phase orthogonal displacement signals produced are completelycompatible with the signal generally found in conventional resolvers asexpressed in EQ. (3).

V _(sin) =E×sin(θ)×sin(ωt)

V _(cos) =E×cos(θ)×sin(ωt)   EQ. (3)

In the following, the implementation of OP-amp circuitry of thedifferential synthesis module (200) is explained in detail.

Differential Synthesis of the Two-Phase Orthogonal Displacement Signals

As illustrated in FIG. 7, in N-phase VR resolver, the differential sinesynthesis module (200A) for V sin signal comprises a group of maximal(N−1)/2 minus-sign sensing resistors, Rsm₁, Rsm₂, . . . , Rsm_(n) (n=1,2, . . . , (N−1)/2), that are connected to the negative (−) input portof the primary OP-amp (Us), and another group of maximal (N+1)/2plus-sign sensing resistors, Rsp₁, Rsp₂, . . . , Rsp_(n) (n=1, 2, . . ., (N+1)/2), that are connected to the positive (+) input port of theprimary OP-amp. The negative input port and the output of OP-amp (Us) isconnected by a primary feedback gain register (RsF), and the positiveinput port and the reference level (ground) is connected by a primarymatch register (RsL).

Likewise, the differential cosine synthesis module (200B) for V cossignal comprises a group of maximal (N−1)/2 minus-sign sensingresistors, Rcm₁, Rcm₂, . . . , Rcm_(n) (n=1, 2, . . . , (N−1)/2), thatare connected to the negative (−) input port of the secondary OP-amp(Uc) and another group of maximal (N+1)/2 plus-sign sensing resistors,Rcp₁, Rcp₂, . . . , Rcp_(n) (n=1, 2, . . . , (N+1)/2), that areconnected to the positive (+) input port of the secondary OP-amp. Thenegative input port and the output of OP-amp (Uc) are connected by asecondary feedback gain register (RcF) and the positive input port andthe reference level (ground) are connected by a secondary match register(RcL).

The sensed signal on the single-wound resolver coil is under-modulatedand includes a certain amount of un-modulated carrier signal. To recoverthe 100% carrier modulated displacement signal, the un-modulated carriersignal must be cancelled out. Thus, the differential OP-amp circuitry of(Us) and (Uc) are constructed so as to the un-modulated carrier signalis regarded and processed as a common mode noise. As the common moderejection ratio (CMRR) of widely used differential OP-amp is generallygreater than 10,000, the signal (b) portion in FIG. 6 is removed throughthe differential OP-amp, whereas effective displacement signal (a)portion is amplified with a certain gain associated with its synthesiscoefficient.

In determining the sensing resistor value in association with thesynthesis coefficient, as an example, its conversion principle isexplained for the case of N=5.

The sensed 5 displacement signals contain their orthogonal displacementsignal components such that sin(θ) signal component in V₁, V₂, V₃, V₄,and V₅ signal is 100%, 30.9%, −80.9%, −80.9%, and 30.9%, respectively,and the cos(θ) signal component in V₁, V₂, V₃, V₄, and V₅ signal is 0%,−95.1%, 58.8%, −58.8%, and 95.1%, respectively. The synthesiscoefficients are optimally selected after solving the system of linearequations by taking the ZF transformation in zero-forcing criterion.

The resultant synthesis coefficients for N=5 case is sine synthesiscoefficients (a1, a2, a3, a4, a5)=(0.4, 0.1236, −0.3236, −0.3236,0.1236) for V sin synthesis and cosine synthesis coefficients (b1, b2,b3, b4, b5)=(0.0, −0.3804, −0.2352, 0.2352, 0.3804) for V cos synthesis.The resultant V sin and V cos, two-phase orthogonal displacementsignals, are synthesized as follows:

V

=0.4*V ₁+0.1236*V ₂−0.3236*V ₃−0.3236*V ₄+0.1236*V ₅

Vcos=0.0*V ₁−0.3804*V ₂−0.2352*V ₃+0.2352*V ₄+0.3804*V ₅

The sensing resistors (R1, R2, R3, R4, R5) represent the absolute valuesof sine synthesis coefficients (a1, a2, a3, a4, a5). To determine thevalues of sensing resistors (R1˜R5, OP-amp input gains), followinggeneralized linear equation can be set:

V _(out)=(a1*V ₁)+(a2*V ₂)+(−a3*V ₃)+(−a4*V ₄)+(a5*V ₅)   EQ. (4)

In EQ. (4), a3 and a4 coefficient is negative and a1, a2, a5 coefficientis positive. Moreover, the sum of two negative coefficients is equal tothat of three positive coefficients, which is one of the uniquecharacteristics of ZF transformation when N is an odd number, andprovides a fundamental condition in realization of the differentialsynthesis. Based on FIG. 7, OP-amp circuitry implementation ofperforming EQ. (4) is shown in FIG. 8.

In determining the values of sensing resistors R1˜R5, feedback gainresistor (RF), and match resistor (RL), let Vout1 be the OP-amp outputsignal by V₁ signal component. Then each OP-amp output signalVout1˜Vout5 by each input signal V₁˜V₅ can be represented by followingequations in EQ. (5-1)˜EQ. (5-5), respectively, after applyingThevenin's theorem and superposition theorem, where “∥” notation denotesthat resistors are connected in parallel.

$\begin{matrix}{{{Vout}\; 1} = {\left( {1 + \frac{RF}{R\; 4\text{}R\; 3}} \right)*\left( \frac{R\; 2{{R\; 5}}{RL}}{{R\; 1} + \left( {R\; 2{{R\; 5}}{RL}} \right)} \right)*V_{1}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}1} \right)} \\{{{Vout}\; 2} = {\left( {1 + \frac{RF}{R\; 4\text{}R\; 3}} \right)*\left( \frac{R\; 1{{R\; 5}}{RL}}{{R\; 2} + \left( {R\; 1{{R\; 5}}{RL}} \right)} \right)*V_{2}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}2} \right)} \\{{{Vout}\; 3} - {\frac{RF}{R\; 3}*V_{3}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}3} \right)} \\{{{Vout}\; 4} = {{- \frac{RF}{R\; 4}}*V_{4}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}4} \right)} \\{{{Vout}\; 5} = {\left( {1 + \frac{RF}{R\; 4\text{}R\; 3}} \right)*\left( \frac{R\; 1{{R\; 2}}{RL}}{{R\; 5} + \left( {R\; 1{{R\; 2}}{RL}} \right)} \right)*V_{5}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}5} \right)}\end{matrix}$

The final output of the Op-amp is the sum of all signals Vout1˜Vout5,and can be expressed as follows:

Vout=Vout 1+Vout 2+Vout 3+Vout 4+Vout 5   EQ. (5-6)

It would be difficult to find the resistor values (R1˜R5, RF, RL)satisfying both EQ. (4) and EQ. (5.1)˜EQ. (5-6) directly. The values ofnegative input port resistors, R3 and R4, in EQ. (5-3) and (5-4) can befound relatively easily. However, calculating the values of the positiveinput port resistors in EQ. (5.1), (5-2), (5-5), requires solving atleast 3 degree system of equations with 3 variables. Furthermore, incases when N is 7 or higher, it would be practically impossible to findthe solution directly. In what follows, simplification is made indetermining the gain resistor values.

Let Rm be the sub-total resistance to the negative (−) input port ofOP-amp, then Rm is the resistance of R3 and R4 in parallel, which can beexpressed as follows:

$\begin{matrix}{{{( - ){Input}\mspace{14mu}{Port}\mspace{14mu}{sub}} - {{total}\mspace{14mu}{Resistance}\text{:}\mspace{14mu}{RM}}} = {{R\; 4\text{}R\; 3} = \frac{R\; 4*R\; 3}{{R\; 4} + {R\; 3}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}7} \right)}\end{matrix}$

Feedback gain resistor (RF) is also connected to the negative (−) inputport of OP-amp in parallel with Rm. Let Ra be the total resistance tothe negative (−) input port of OP-amp, then Ra becomes,

$\begin{matrix}{{( - ){Input}\mspace{14mu}{Total}\mspace{14mu}{Resistance}\text{:}\mspace{14mu}{Ra}} = {{R\; 4{{R\; 3}}{RF}} = \frac{R\; 4*R\; 3*{RF}}{{R\; 4*R\; 3} + {R\; 4*{RF}} + {R\; 3*{RF}}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}8} \right)}\end{matrix}$

Likewise, total resistance to the positive (+) input port of OP-amp, Rb,becomes,

$\begin{matrix}{{( - ){Input}\mspace{14mu}{Total}\mspace{14mu}{Resistance}\text{:}\mspace{14mu}{Rb}} = {{R\; 1{{R\; 2}}R\; 5\text{}{RL}} = \frac{R\; 1*R\; 2*R\; 5*{RL}}{\begin{matrix}{{R\; 1*R\; 2*R\; 5} + {R\; 1*R\; 2*{RL}} +} \\{{R\; 2*R\; 5*{RL}} + {R\; 1*R\; 5*{RL}}}\end{matrix}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}9} \right)}\end{matrix}$

When R1 is excluded, the sub-total resistance to the positive (+) inputport of OP-amp, Rb1, becomes,

$\begin{matrix}{{( + ){Input}\mspace{14mu}{Total}\mspace{14mu}{{Resistance}\left( {R\; 1\mspace{14mu}{is}\mspace{14mu}{Excluded}} \right)}\text{:}\mspace{14mu}{Rb}\; 1} = {{R\; 2{{R\; 5}}{RL}} = \frac{R\; 2*R\; 5*{RL}}{{R\; 2*R\; 5} + {R\; 2*{RL}} + {R\; 5*{RL}}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}10} \right)}\end{matrix}$

When R2 is excluded, the sub-total resistance to the positive (+) inputport of OP-amp, Rb2, becomes,

$\begin{matrix}{{( + ){Input}\mspace{14mu}{Total}\mspace{14mu}{{Resistance}\left( {R\; 2\mspace{14mu}{is}\mspace{14mu}{Excluded}} \right)}\text{:}\mspace{14mu}{Rb}\; 2} = {{R\; 1{{R\; 5}}{RL}} = \frac{R\; 1*R\; 5*{RL}}{{R\; 1*R\; 5} + {R\; 1*{RL}} + {R\; 5*{RL}}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}11} \right)}\end{matrix}$

When R5 is excluded, the sub-total resistance to the positive (+) inputport of OP-amp, Rb5, becomes,

$\begin{matrix}{{( + ){Input}\mspace{14mu}{Total}\mspace{14mu}{{Resistance}\left( {R\; 5\mspace{14mu}{is}\mspace{14mu}{Excluded}} \right)}\text{:}\mspace{14mu}{Rb}\; 5} = {{R\; 1{{R\; 2}}{RL}} = \frac{R\; 1*R\; 2*{RL}}{{R\; 1*R\; 2} + {R\; 1*{RL}} + {R\; 2*{RL}}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}12} \right)}\end{matrix}$

Now the Vout1 in EQ. (5.1) can be factored into two components: theinput signal divider and the feedback component as expressed in EQ.(5-13).

$\begin{matrix}{{{Output}\mspace{14mu}{by}\mspace{14mu} V\; 1\mspace{14mu}{{Signal}:{{Vout}\; 1}}} = {{\left( {1 + \frac{RF}{R\; 4\text{}R\; 3}} \right)*\left( \frac{R\; 2{{R\; 5}}{RL}}{{R\; 1} + \left( {R\; 2{{R\; 5}}{RL}} \right)} \right)*V_{1}} = {({Feedback\_ Component})*\left( {{Input\_ Signal}{\_ Divider}} \right)*V\; 1}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}13} \right)}\end{matrix}$

The Feedback_Component can be calculated as follows by using EQ. (5-7)and EQ. (5-8):

$\begin{matrix}{{\left( {1 + \frac{RF}{R\; 4\text{}R\; 3}} \right){RF}*\left( {\frac{1}{RF} + \frac{{R\; 4} + {R\; 3}}{R\; 4*R\; 3}} \right)} = {{RF}*\left( \frac{{R\; 4*R\; 3} + {R\; 4*{RF}} + {R\; 3*{RF}}}{R\; 4*R\; 3*{RF}} \right)}} & {{EQ}.\mspace{14mu}\left( {5\text{-}14} \right)}\end{matrix}$

Likewise Input_Signal_Divider can be calculated as follows by using EQ.(5-9) after multiplying R1 to both numerator and denominator:

$\begin{matrix}{\left( \frac{R\; 2{{R\; 5}}{RL}}{{R\; 1} + \left( {R\; 2{{R\; 5}}{RL}} \right)} \right) = {{\frac{1}{R\; 1}*\left( \frac{R\; 1*R\; 2*R\; 5*{RL}}{\begin{matrix}{{R\; 1*R\; 2*R\; 5} + {R\; 1*R\; 2*{RL}} +} \\{{R\; 2*R\; 5*{RL}} + {R\; 1*R\; 5*{RL}}}\end{matrix}} \right)} = {{\frac{1}{R\; 1}*R\; 1{{R\; 2}}R\; 5\text{}{RL}} = \frac{Rb}{R\; 1}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}15} \right)}\end{matrix}$

Therefore, Vout1 can be rewritten by applying EQ. (5-14) and EQ. (5-15)to EQ. (5-13), and as follows:

$\begin{matrix}{{{Vout}\; 1} = {\frac{RF}{Ra}*\frac{Rb}{R\; 1}*V_{1}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}16} \right)}\end{matrix}$

As a specific case, when Ra=Rb, then EQ. (5-16) is simplified asfollows:

$\begin{matrix}{{{Vout}\; 1} = {\frac{RF}{R\; 1}*V_{1}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}17} \right)}\end{matrix}$

Applying the assumption of Ra=Rb in EQ. (5-17) implies that the sum ofall input voltages to the negative (−) input port is the same as that ofall input voltages to the positive input port, and that the feedbackresistor and the match resistor have the same value. Here, the uniquecharacteristics of ZF transformation fully satisfy the specific Ra=Rbcondition: the sum of all coefficients is zero, and the sum of allnegative coefficients and the sum of all positive coefficients areequal. Therefore, if the feedback gain resistor (RF) and the matchresistor (RL) in FIG. 8 are set to have the same resistance, then EQ.(5.1) can be simplified to EQ. (5-17).

The similar approach can be applied to Vout2 and Vout5 signal in FIG. 8,and can be simplified as follows:

$\begin{matrix}{{{Vout}\; 2} = {{\frac{RF}{Ra}*\frac{Rb}{R\; 2}V_{2}} = {\frac{RF}{R\; 2}*V_{2}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}18} \right)} \\{{{Vout}\; 5} = {{\frac{RF}{Ra}*\frac{Rb}{R\; 5}V_{5}} = {\frac{RF}{R\; 5}*V_{5}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}19} \right)}\end{matrix}$

Combining all Vout1˜Voutb 5 signals, the output of OP-amp Vout in EQ.(5-6) can be also simplified as follows:

$\begin{matrix}{{Vout} = {{{{Vout}\; 1} + {{Vout}\; 2} + {{Vout}\; 3} + {{Vout}\; 4} + {{Vout}\; 5}} = {{\frac{RF}{R\; 1}*V_{1}} + {\frac{RF}{R\; 2}*V_{2}} - {\frac{RF}{R\; 3}*V_{3}} - {\frac{RF}{R\; 4}*V_{4}} + {\frac{RF}{R\; 5}*V_{5}}}}} & {{EQ}.\mspace{14mu}\left( {5\text{-}20} \right)}\end{matrix}$

EQ. (5-20) shows that when the signals are simultaneously input to thenegative and positive input port of Op-amp, the gain for each inputsignal is determined by the ratio between the feedback resistor valueand the input resistor value under a specific condition of Ra=Rb andRF=RL. Therefore, once the coefficients in EQ. (4) are determined, eachsensing resistor value R1˜R5 in FIG. 8 is determined by the followingratio: R1=RF/a1, R2=RF/a2, R3=RF/a3, R4=RF/a4, R5=RF/a5.

In summary, when the multi-phase VR resolver generates either amplitudeunder-modulated or 100% modulated N-phase displacement signals by Nexcitation-sensing coil-poles placed at phase-angle positions evenlydivided by an odd number N (N≥5) over one period of electrical angle ormechanical angle, the common mode noise or un-modulated carrier signalcomponent can be removed and two-phase orthogonal displacement signalsare obtained by the differential synthesis, which is realized by thedifferential Op-amp circuitry. The values of the sensing resistors areconveniently determined by the ratio of the value of OP-amp feedbackgain register to the corresponding synthesis coefficients.

The foregoing disclosures and explanations are for the genericmulti-phase VR resolver topology in which each excitation-sensing coilis single-wound at each pole; however, other types of coil-windings canbe used to achieve superior performances.

The Balance-Wired Multi-Phase Resolver

In the balance-wired multi-phase VR resolver, each single-wound Nexcitation-sensing coil in the generic N-phase VR resolver is subdividedinto k number of coils, and the k× speed of rotor lobe is installed,where k is greater than or equal to 2. The k subdividedexcitation-sensing coils are connected serially with alternatingpolarity. A magnetic flux balance is achieved between two coils havingalternating polarities. Here, even-numbered k subdivided coils providethe full balanced flux; however, odd-numbered coils would still providean almost balanced flux from the overall resultant flux layout of theodd-numbered N-phase on the stator. The k subdivided coils are alignedwith every rotor lobe at the same electrical angle positions, andgenerate one phase-delayed displacement signal under the balanced flux.Thus, N sequentially phase-delayed and amplitude modulated displacementsignals are obtained from N sets of k subdivided coils that are seriallyconnected. The magnetic flux balance from multiple layers through thebalance-wired coils results in a more precise position accuracy.

Compared with the single L1, L2, . . . , Ln excitation-sensing coil inFIG. 3A, in FIG. 9A, each coil is subdivided into two coils (k=2), Lo1and Le1, Lo2 and Le2, . . . , Lon and Len. Physically, Lo and Le ispositioned at symmetrically with 180° mechanical angle offsets. Althoughtwice coil-windings are required compared to the generic single-woundresolver, the magnetic flux is balanced well with each other as the fluxϕ_(o1), ϕ_(o2), . . . , ϕ_(on) and the flux ϕ_(e1), ϕ_(e2), . . . ,ϕ_(en) have the same magnitude, but 180° out of phase with each other,respectively. The topology of balance-wired multi-phase VR resolveroffers a realization of the precise k× speed resolver.

When the resolver is configured to operate at k× speed, the totalelectrical angle is expanded to k*360° per one mechanical turn by the k×teeth rotor lobe. For example, when k is 2 for 2× teeth lobe, onemechanical turn(360°) yields two electrical cycles (2×360°). Therefore,the subdivided k coils should be placed at the same electrical anglepositions of the k× teeth rotor lobe.

As an example, FIG. 9B illustrates the structure of the balance-wiredmulti-phase VR resolver for N=5 and k=2, where 2× sinusoidal-waveformrotor (102) lobe is installed. As can be seen in this figure, Lo1 of L1is located at 0° and Le1 of L1 is symmetrically located at 180° positionin mechanical angle (but both are 0° in electrical angle since the rotorlobe is 2×). Lo2 of L2 is located at 72° and Le2 of L2 is at 72+180=252°in mechanical angle (both 72° in electrical angle), and so on for L3,L4, and L5. The signal processing of the balance-wired multi-phase VRresolver is the same as that of single-wound case, as shown in FIG. 3B.

The balance-wired multi-phase VR resolver in FIG. 9B has the sameelectrical characteristic as that of the single-wound in FIG. 3B, but itprovides a superior performance and relaxes the manufacturing tolerancesof the rotor lobe.

In a balance-wired multi-phase WR resolver, each N sensing coil-poles ofthe N-phase WR resolver is subdivided into a plural number of coils thatcan be distributed along the stator such as to be magnetic flux balancedover the corresponding rotor installed.

The Dual Stator Balance-Wired Resolver

In the above balance-wired multi-phase VR resolver, all subdivided coilsare distributed along the single magnetic flux path formed by a pair ofstator and rotor. However, subdivided coils can be distributed along themultiple magnetic flux paths formed by multiple pairs of stators androtors.

As an example, two (k=2) subdivided coils are separately placed on onepair of stators (101 and 103) on the shared axis and rotors (102 and104) in FIG. 9C, where two subdivided coils are serially connected andplaced at the same electrical angle position with an opposite electricalpolarity. The rotor is composed of rotor A (102) and rotor B (104) thathave an identical rotor lobe and share a common rotational body with thesame electrical angle, and further can be integrated into a singlerotor. A set of divided coils, Lo1, Lo2, . . . , Lon, generates flux,ϕ_(o1), ϕ_(o2), . . . , ϕ_(on), such as the magnetic flux path #A formedby the stator A (101) and the rotor (102), whereas the other set ofdivided coils, Le1, Le2, . . . , Len, generates flux, ϕ_(e1), ϕ_(e2), .. . , ϕ_(en), such as the magnetic flux path #B formed by the stator B(103) and the rotor (104), where the dual magnetic flux paths areindependently formed and balanced.

The advantage of employing dual stators is that aside from the desireddisplacement signals, all common mode noise induced from the directionalexternal magnetic flux toward each coil pairs on the stators effectivelycancel each other out. Therefore, the displacement signal without commonmode noise is attained through each pair of subdivided coils on the dualstators over the dual paths of magnetic flux.

The Double-Wound Multi-Phase VR Resolver

Another type of multi-phase VR resolver topology to be disclosed is thedouble-wound coil-windings for each excitation-sensing coil. Eachexcitation-sensing coil in the generic single-wound multi-phase VRresolver is separated into the primary excitation coil and the secondarysensing coil.

Referring to FIG. 9D, an exemplary schematic circuit diagram of thedouble-wound multi-phase VR resolver is drawn, where Nexcitation-sensing coils are separated into N primary excitation coils(Lp1, Lp2, . . . , Lpn) and N secondary sensing coils (Ls1, Ls2, . . . ,Lsn), thereby achieving Galvanic isolation by completely isolating theelectric paths of the primary coils and the secondary coils.

With a certain ratio of number of winding turns between the primary andthe secondary coils, all primary coils (or all secondary coils) have thesame number of winding turns with an identical electrical polarity. Theflux balance is maintained within all primary excitation coils andwithin all secondary sensing coils independently.

As the rotor rotates, the phase-delayed amplitude modulated displacementsignals, V₁, V₂, . . . , V_(N), are sensed at the secondary sensingcoils, Ls1, Ls2, . . . , Lsn, under the excitation of driving signal atthe primary coils, Lp1, Lp2, . . . , Lpn, respectively.

The Multi-Phase Variable Inductance Resolver

The multi-phase VR resolvers so far disclosed are constructed in asingle body stator, integrating all coil-poles in one contiguous statorbody. The magnetic flux generated by excitation or sensing coils isshared commonly among all magnetic circuits. However, the odd-numbered Ncoil-poles of the multi-phase VR resolver topology has a distinctcharacteristic such that the flux generated from each coil-pole does notinterfere with the flux generated from the other coil-poles. Eachcoil-pole, which exists and operates independently, on the stator, canbe placed non-contiguously from the other coil-poles. Consequently, eventhough N coil-poles are separated into N physical stator-bodies, itstill legitimately generates N phase-delayed displacement signals uponthe varying inductance at each coil-pole, as long as a suitable magneticflux variation is maintained between the N separated stators and therotor lobe.

In FIG. 9E, as an exemplary illustration, 5-phase variable inductanceresolver configuration is shown, where 5 stators are disjointly placedon the printed circuit board (PCB). It comprises a rotor and 5 separatedstators (Stator_0, Stator_72, Stator_144, Stator_216, Stator_288) onwhich 5 excitation-sensing coils (Coil_0, Coil_72, Coil_144, Coil_216,Coil_288) are wound. The magnetic circuit formed at each coil-pole staysbetween each stator and rotor lobe, independently from the otherstators.

The separated stators can be fixed either on the PCB or around the rotorthrough other structures. FIG. 9F shows an exemplary inductancevariation of the inductive resolver with 5 coil-poles on the separatedstators that is successively 72° shifted with varying inductance between7.8 mH˜9.5 mH to the rotational angle of the rotor lobe at each coil.

When stators or rotors are implemented on the PCB, stator coils can bereplaced by printed coil patterns. The stator cores can be replaced byother means that provide the optimal airgap and permeance depending ondesign factors such as the stator structure and its materials, the rotorshapes and its materials, or the excitation frequency that is as high asseveral hundred Hz to several MHz. Therefore, various kinds ofmulti-phase inductance resolvers are feasible to attain effectivemulti-phase displacement signals through varying inductance between thestator and the rotor.

FIG. 9G illustrates an exemplary PCB type stator, in which 5 printedcoil patterns having a circular sector shape are evenly placed with 72°phase-angle on the PCB, in which iron plates having an appropriatepermeability may be attached on the other side of the board. In FIG. 9H,an exemplary 1× rotor lobe in combination with the stator implemented bycoil patterns on PCB is illustrated, where the rotor lobe is attached tothe stator PCB in parallel with a certain airgap.

The Multi-Phase Magnetic Resolver

The topology of odd-numbered N sensors and differential synthesis isalso applicable to the magnetic resolver (or encoder) having magneticposition sensors such as magneto-electric or magneto-resistive sensors.The N magnetic position sensors are placed at evenly placed electricalangle positions over one mechanical or electrical period of the stator,where at least one electrical period is formed on the stator by magnetsof the rotor (or mover). The N sequentially phase-delayed displacementsignals, where N is an odd number greater than or equal to 5, areattained and the two-phase orthogonal displacement signals aresynthesized by the differential synthesis module, where the common modenoise induced from the external disturbance flux is also removed bycommon mode rejection of the differential OP-amp circuitry. Aselectrical noise is very critical in resolver applications, thedifferential synthesis is a very effective solution against the heavyelectrical noise.

FIG. 9I illustrates a functional diagram of the typical 5-phase magneticresolver. As the rotor being displaced, sequentially 5 phase-delayeddisplacement signals, V1, V2, V3, V4, and V5 are sensed from 5 sensors(H1, H2, H3, H4, and for H5) upon the magnetic variations of theresolver body (100). The differential synthesis module (200) comprises adifferential sine synthesis module (200A) and a differential cosinesynthesis module (200B) in FIG. 9I, which has the same circuitry in FIG.7 (or FIG. 8). Further, in some specific applications such as a linearresolver, the sensors, H1˜H5, can be placed on the rotor (mover) todetect displacement signals upon the variations of magnets of thestator.

Rotor Lobe of Quasi-Square Waveform Saliencies

As rotor lobe saliencies directly affect the shape of resolver outputsignal, the rotor lobe requires a sophisticated design and a highprecision manufacturing process in order to produce a precisedisplacement signal.

U.S. Pat. No. 6,137,204 discloses a curved shaped rotor lobe whoseairgap permeance varies in accordance with a sinusoidal function as therotor rotates. U.S. Pat. No. 7,030,532 B2 discloses a more complicatedequation in designing rotor lobe saliencies that achieves an airgaphaving a pure sinusoidal varying property. However, a sophisticatedshape of rotor saliencies would entail either an increase inmanufacturing cost or problems in quality control, especially for 1×rotor lobe.

In International Application Publication No. WO 2020/149489, thefollowing are disclosed: when N phase-delayed displacement signals arequasi-square waveforms that are sensed on magnetic sensors, and thesensed signals are ZF transformed, then the two-phase orthogonaldisplacement signals are stair step signals, of which the Lissajousgraph is the shape of a 2N-gon; an accurate position information isdetermined after compensating the error signal between the 2N-gon andthe pure circle by a piece-wise linear approximation technique, which isknown a priori.

The resolver is very unique and delicate analog equipment that isvulnerable to any impairments, interference or noise. However, the rotorlobe having quasi-square waveform saliencies produces a digital typesignal that is generally more robust under harsh environment. In thisregard, a specific shape of rotor lobe is disclosed to produce aquasi-square waveform signal (or trapezoidal signal). An exemplary rotorlobe of the quasi-square waveform is shown in FIG. 10A that is installedin single-wound 11-phase VR resolver topology.

The rotor lobe circumference having quasi-square waveform saliencies islargely divided into 2 sections; a constant airgap (between the statorand rotor lobe) section of T1 (arc shape), and a linearly varying airgapsection of T2 (slope shape). T1 can be divided into two sections, T11and T12, which have different radii from each other. T11 has a largerradius than T12, so the signal amplitude induced by T11 is bigger thanthe one by T12. T2 can also be divided into two sections, T21 and T22,both of which have identical slopes, but in opposite directions. T21 andT22 are symmetrically located at opposite sides. Since the T21 and T22airgap is narrower, the signal induced by T21 and T22 varies quickly atthe opposite direction.

The resultant quasi-square (or trapezoidal) waveform signal is shown inFIG. 10B. As the rotor rotates, the arc shaped section (T11 or T12) ofthe rotor lobe produces either a higher or lower level signal upon thetwo different radii; T11 produces the higher level signal and T12produces the lower level signal. The slope shaped section (T21 or T22)produces either a rising edge signal (T21) or falling edge signal (T22).

The signal sensed by the rotor lobe of quasi-square waveform saliencies(hereinafter referred to as “quasi-square waveform rotor lobe”) is anamplitude modulated signal by the excitation carrier as shown in FIG.10C, but its envelope is quasi-square waveform as shown in FIG. 10B. The11-phase VR resolver will generate successively 32.73° phase-delayeddisplacement signals, V₁, V₂, . . . , V₁₁, of which envelopes are thequasi-square waveforms.

To obtain the two-phase orthogonal displacement signals, those 11-phasedisplacement signals, V₁, V₂, . . . , V₁₁, are fed into the differentialsynthesis module (200) in FIG. 5. The resultant synthesis equation iscalculated from the ZF Transformation as follows:

$\begin{matrix}{{{V\;\sin} = {{0.1820*V_{1}} + {0.1531*V_{2}} + {0.0756*V_{3}} - {0.0258*V_{4}} - {0.1191*V_{5}} - {0.1746*V_{6}} - {0.1746*V_{7}} - {0.1192*V_{8}} - {0.0259*V_{9}} + {0.0756*V_{10}} + {0.1526*V_{11}}}}{{V\;\cos} = {{0.0983*V_{2}} + {0.1652*V_{3}} + {0.1798*V_{4}} - {0.1372*V_{5}} - {0.0511*V_{6}} - {0.0513*V_{7}} - {0.1374*V_{8}} - {0.1798*V_{9}} - {0.1652*V_{10}} + {0.0989*V_{11}}}}} & {{EQ}.\mspace{14mu}(6)}\end{matrix}$

The calculated orthogonal V sin and V cos signal waveform of EQ. (6) isshown in FIGS. 10D and E, respectively, of which envelope is very closeto sin(θ) and cos(θ) signal, respectively. To check the orthogonality ofthe V sin and V cos signals, the Lissajous graph is drawn in FIG. 10F,which shows that the outline of the Lissajous graph is a circle shape.The Lissajous graph after removing the carrier is drawn in FIG. 10G, andas expected, the shape is more precisely a 22-gon (2×11-gon). Furthercompensation processing can improve the accuracy of position detectionin the orthogonal signals as noted earlier.

As a reference, in FIG. 10H, the Lissajous graph of two quasi-squarewave orthogonal signals is drawn, which are directly obtained from theconventional VR resolvers. As expected, its shape is quite close to thesquare, which cannot produce any meaningful absolute positioninformation.

In FIG. 11A, the conventional rotor (102) lobe whose saliencies producea sinusoidal signal (hereinafter referred to as “sinusoidal-waveformrotor lobe”) is installed in single-wound 11-phase VR resolver.Certainly, a well-designed sinusoidal-waveform rotor lobe would producea more precise sinusoidal signal, which results in more accurateposition detection. However, when taking into consideration thedifficulties in manufacturing a well-grounded sinusoidal-waveform rotorlobe, the quasi-square waveform rotor lobe is more advantageous.

The Multi-Speed (k×) Multi-Phase VR Resolver

As the number of coil-poles increases, a superior performance of themulti-phase VR resolver is expected. A higher speed of k× multi-phase VRresolver is preferred as well in order to achieve a higher accuracy ofposition detection.

In some applications, however, the multi-phase VR resolver needs to beoperated at a higher speed of k× without increasing the number ofcoil-poles. In this regard, a certain type of multi-phase VR resolvertopology can be constructed.

Usually in conventional resolvers, the matched configuration of thestator and the rotor lobe is required for the k× speed realization, andthe k× speed operation is attained by employing the rotor lobe whosesaliencies produce k-times of electrical period per one mechanical turn.This kind of approach makes it hard to install a various k× speed ofrotor interchangeably in a fixed stator configuration because aparticularly designed electrical angle deviation is necessary betweeneach stator coil-pole and the angle of rotor lobe saliencies. However,the angle deviation between the rotational mechanical angle of the rotorlobe and the electrical angle is limited to some specific values, wherethe electrical angle is formed by the coil-winding configuration of theexcitation coil, sine sensing coil, and cosine sensing coil. In X. Ge etal. (“A Novel Variable Reluctance Resolver with NonoverlappingTooth-Coil Windings,” IEEE Trans. Energy Conversion, vol. 30, no. 2,June 2015), for instance, a VR resolver operated at three kinds of speedin the same stator configuration is realized by introducing aconfiguration of nonoverlapping tooth-coil windings on the stator.

On the other hand, the multi-phase resolver topology flexibly realizesvarious k× speeds by simply installing the rotor lobe of k teeth(saliencies) in a fixed stator configuration. One restriction is thatwhen the k× (k is less than N) speed is considered in the N-phase VRresolver configuration, the angle between the rotor teeth (saliencies)becomes D=360°/k, then D cannot be an integer multiple of phase-divisionangle (360°/N). In other words, when N is an odd number, 1×˜(N−1)× speedof rotor lobe saliencies are available, except for the speed of N′snon-trivial divisors and their multiples (or equivalently, k cannot be anon-trivial divisor of N and k cannot be a multiple of any non-trivialdivisor of N).

As an exemplary configuration, FIG. 11A shows the 1× VR resolver withN=11 coil-poles on the stator, in which any speed (k=1˜10) of the rotorlobe can be installed interchangeably since N=11 is a prime number.FIGS. 11A to J illustrate all possible 1×˜10× speeds of 11-phase VRresolver configurations installed with rotor lobe having 1˜10 teeth(saliencies). There are k teeth (saliencies) at 360°/k phase-anglepositions in one mechanical turn, resulting in no phase overlap withphase-division angle of the stator coil.

As the electrical angle is expanded by k*360° per one stator mechanicalturn in the k× speed resolver, the electrical angle needs to take modulo360° when the angle is over 360°. Therefore, the signal mapping from thecoil-pole position to the differential ZF synthesis module, namely L1,L2, . . . , L11 to OP-amp input index V₁, V₂, . . . , V₁₁ needs to beshifted according to k in EQ. (6). Those shifted V₁, V₂, . . . , V₁₁signals are differentially synthesized (200) in the same way the 1×multi-phase VR resolver does. The resolver transfer ratio (K) in EQ. (2)also varies as the teeth number k of rotor lobe varies.

Since the design and manufacturing of the sinusoidal k× speed rotor iscomplex, the k× speed quasi-square waveform saliency rotor lobe can alsobe advantageously used as described in the foregoing sections.

Additionally, for some applications, the resolver needs to operate attens of multiple speeds on a small size stator that cannot incorporatemany coil-poles due to its limited space. In this case, referring to the5-phase VR resolver in FIG. 11K, the angle between the stator teeth (101a) and rotor teeth (102 a) is configured to be successively ⅕^(th)period deviated at each coil-pole tooth.

When the k× speed of N-phase resolver is considered, one rotor tooth isregarded as one electrical period of 360°, and the teeth on each statorcoil are constructed such that the angle between the rotor teeth (102 a)and the stator teeth (101 a) is successively 0/Nth, 1/Nth, 2/Nth , 3/Nth, . . . , to N−1/Nth teeth period delayed through N stator coil-polesplaced around the stator.

In detail, in FIG. 11K, 5 sensing coils (L1, L2, L3, L4, L5) are placedat evenly spaced positions around the stator (101), and k rotor teeth(102 a) lobe are formed around the rotor (102). Each sensing coil hasseveral stator teeth (101 a), then each rotor tooth period can beregarded as one electrical period of 360°. The stator teeth (101 a) oneach of the 5 stator coil-poles are configured to successively ⅕^(th)period delayed, i.e., 0/5^(th) teeth delay at L1, and ⅕^(th), ⅖^(th)⅗^(th) ⅘^(th) teeth delay at L2, L3, L4, L5, respectively. Therefore, 5sequentially phase-delayed displacement signals are sensed at 5 statorcoil-poles with k× speed over one mechanical turn as the rotor rotates.In practical applications, k would be greater than or equal to 15 andthe number of teeth on each stator would be around 2˜10.

So far, the explanations, exemplary illustrations and drawings regardedthe rotary resolvers with in-rotor configuration, but the presentinvention can also be equally applied to the out-rotor configuration aswell as to the linear resolvers.

The Demodulation and Carrier Recovery of Amplitude ModulatedDisplacement Signals

As digital circuit technology advances, digital processor or applicationspecific integrated circuit (ASIC) can be advantageously used to processthe signal of multi-phase VR resolver after A/D conversion. The resolveroutput signal, amplitude modulated by the excitation signal carrier, isfirstly A/D converted. In removing the carrier signal component, theHilbert Transform can be conveniently applied to the resolver signal.

The V sin and V cos signal, the output of the differential ZF synthesismodule (200), can be processed by a commercially available R/D converter(300) to calculate the position information. Phase sensitivedemodulation may also be applied when the excitation signal frequency isvery high or when high speed signal processing is required to minimizethe delay.

In FIG. 12A, an exemplary demodulation by Hilbert Transform is shown.Hilbert Transformer (112, 122) shifts only the phase of carrier sin(ωt)by 90° in V sin=E*sin(θ)*sin(ωt) and V cos=E*cos(θ)*sin(ωt) as thedisplacement frequency of the envelope of V sin and V cos is much lowerthan that of the carrier signal. The output signal of HilbertTransformer is added to the original signal, of which carrier phase isnot shifted, at the Adder (113, 123). The absolute value is taken fromthe complex signal of the Adder output at the Absolute Calculator (114,124). The position (θ) of the resolver is calculated by taking thearctangent of V sin_demod/V cos_demod at the Arc Tangent Calculator(120).

FIG. 12B shows an exemplary diagram of the circuit that extracts thecarrier signal from N-phase amplitude modulated displacement signals.All V₁, V₂, . . . , V_(N) signals are amplified by the same gain, andadded to the negative port of Op-amp adder (U3). When all coefficientresistor values are set to equal, R1=R2= . . . =Rn, and let the feedbackgain resister be Rg, then the pure un-modulated carrier signal componentis recovered as the sum of all N-phase displacement signals is zerounder the ideal condition.

The amplitude of the recovered un-modulated carrier represents the fluxbalance status of the magnetic circuit formed in thestator-airgap-rotor, and should be constant under the ideal condition.However, in practical realizations, the amplitude will deviate from theconstant value depending on airgap eccentricity between the rotor lobeand the stator, or mechanical error, or misalignment, etc.

By utilizing this constant amplitude property, the recovered carriersignal can be utilized in evaluating the manufacturing accuracy or inadjusting or fine tuning the multi-phase VR resolver. When the phasesensitive demodulation is executed, the recovered carrier signal canserve as a reference signal as well.

The Multi-Phase Synchro

In general, synchros output three-phase displacement signals that areoffset by 120° phase, whereas resolvers output two-phase orthogonalsignals with 90° offset. Synchro transmitter is widely used in remotecontrol, manipulation, or monitoring system applications in combinationwith synchro receiver. In FIG. 12C, a multi-phase VR synchro isexemplarily drawn, where carrier modulated three-phase displacementsignals of sin(θ)sin(ωt), sin(θ−120°)sin(ωt), and sin(θ−240°)sin(ωt),can be generated from the N-phase displacement signals.

The multi-phase synchro comprises of the resolver body (100) and threedifferential synthesis modules of 200A, 200C, and 200D, forsin(θ)sin(ωt), sin(θ−120°)sin(ωt), and sin(θ−240°)sin(ωt) generation,respectively. The sin(θ)sin(ωt) synthesis module (200A) is the same asthat of in FIG. 5. The sin(θ−120°)sin(ωt) synthesis module (200C) andsin(θ−240°)sin(ωt) synthesis module (200D) is implemented by anidentical OP-Amp circuitry of 200A except the synthesis coefficients,namely the sensing resistor values, which can be calculated by the ZFtransformation. The amplitude of the multi-phase synchro output signalis also adjusted by a gain of 200A, 200C, and 200D modules. The outputsignals, V_(sin 0), V_(sin 120), and V_(sin 240), are the three-phasedisplacement signals typically found in synchro transmitters.

The Multi-Phase Wound-Rotor (WR) Resolver

The novel topology of multi-phase VR resolver can be equally applied tothe wound-rotor (WR) type resolvers as they share the basic operationalprinciple. In the WR resolver, the rotor is wound by an excitation coilthat has a sinusoidally distributed winding instead of the rotor lobe inVR resolver. In FIG. 12D, an exemplary topology of 5-phase WR resolveris drawn, where the primary (excitation) coil (Lp) is wound on the rotor(102) and 5 secondary (sensing) coils (Ls1, Ls2, . . . , Ls5) are woundon the stator (101) at evenly spaced positions. In general, a brush orring transformer is used in applying the driving carrier signal to Lp.As for the case of the conventional WR resolvers, the excitation coil(Lp) has a sinusoidally distributed winding on the rotor such thatsingle or multiple electrical periods of sinusoidal signals aregenerated on the stator per one turn of the rotor from the varyingmutual inductances between the excitation coil and sensing coils.

As the rotor rotates by θ°, amplitude modulated 5 sequentiallyphase-delayed displacement signals, V1, V2, . . . , V5, are induced onthe 5 sensing coils, where un-modulated carrier signal may be includeddepending on the specific rotor windings. In conventional WR resolvers,in order to achieve precise and 100% amplitude modulation, techniqueslike skewing the core construction, damper winding, or increased numberof coil-poles distribution are employed in removing the harmonicfrequencies, which is a major cause of distortion in sensingdisplacement signals. In multi-phase WR resolvers, the complicatedtechniques can be avoided as the final two-phase phase displacementsignals are optimally synthesized on synthesis coefficients from themulti-phase sensed signals. Accordingly, as the complicated coilwindings and techniques to remove the harmonics are circumvented, thesize of multi-phase WR resolver is reduced and its manufacturing processbecomes more simplified.

When each of the N sensing coils are subdivided into a plural number ofcoils, a balance-wired WR resolver is also feasible by connectingserially the subdivided coils that are located at 180° difference inmechanical or electrical angle on the stator with alternating polarityto balance the magnetic flux, where the subdivided coils can bedistributed along single stator or dual stators to increase thedirectional anti-noise performance anti-noise performance.

The Multi-Phase Capacitive Resolver

The conventional resolvers or multi-phase VR resolvers so far disclosedsense the inductive variations of coils upon the displacement of therotor. Capacitive resolvers (or encoders) sense the capacitivevariations between the stator electrodes and the rotor electrodes. Ingeneral, the conventional capacitive encoders output amplitude modulatedtwo-phase orthogonal displacement signals directly from the electrodesof capacitive sinusoidal patterns on the stator or the rotor.

FIG. 12E illustrates an exemplary topology of multi-phase capacitiveresolver body for 5-phase case, where 5 stator electrodes (stator0,stator72, stator144, stator216, and stator288), are spaced at 72°intervals. The rotor electrode is installed in parallel to the statorelectrodes with a thin airgap around the rotational shaft. The statorelectrodes behave as capacitive elements, and the capacitance ofcapacitive element C0, C72, C144, C216, and C288, is set to besinusoidally proportional to a shared area between the rotor andstator0, stator72, stator144, stator216, and stator288, respectively.Thus, the stator electrodes and rotor lobe electrode are designed suchthat the capacitance of capacitive elements varies sinusoidally on therotor displacement.

FIG. 12F shows a functional and differential synthesis circuitry diagramof the 5-phase capacitive resolver. When the carrier signal of a fewhundred to a few mega-hertz is applied to the rotor and the stator, asthe rotor rotates, sequentially 5 phase-delayed and under-modulateddisplacement signals, V1, V2, V3, V4, and V5 are sensed on detectiondevice, Z1, Z2, Z3, Z4, and Z5, respectively, upon the capacitivevariations on the resolver body (100), in response to the displacementbetween the rotor electrode and stator electrodes.

The differential synthesis module (200A and 200B) in FIG. 12F has thesame circuitry in FIG. 7 (or FIG. 8), and in which the un-modulatedcarrier signal, shown in FIG. 6, is removed with common mode rejectionas described in earlier sections.

The Exemplary Fabrication of 9-Phase VR Resolvers

The novel multi-phase resolver topology, and the method and apparatus ofits signal processing presented in the invention, is evaluated andverified by the fabricated two types of multi-phase VR resolvers and twotypes of rotor lobes: the single-wound 9-phase VR resolver and thebalance-wired 9-phase VR resolver; the 1× quasi-square waveform saliencyrotor lobe and the 4× sinusoidal-waveform saliency rotor lobe.

The stator is made of lamination-coated and stacked electrical steel, ofwhich the radius is 150 mm and the height is 50 mm. As illustrated inFIG. 3A, the 9 coil-poles single-wound VR resolver is fabricated, inwhich each of the 9 excitation-sensing coil windings has around 10 mHinductance and is wound with the same polarity, located evenly at 40°phase-angle positions over one period of the stator.

FIG. 9A illustrates the balance-wired 9-phase VR resolver. Here, twice(9×2=18) of excitation-sensing coil-poles are evenly placed with 20°spacing over one period of the stator.

The quasi-square waveform rotor lobe with 1× speed, as illustrated inFIG. 10A, is fabricated. The sinusoidal-waveform rotor lobe with 4×speed, as illustrated in FIG. 11D, is fabricated.

The differential synthesis module is implemented on the PCB bydifferential OP-amp circuitry, where 10 kHz carrier frequency ofexcitation signal is applied, and R/D converter of commerciallyavailable AD1210 (Analog Device) R/D converter is used.

In FIG. 13A and FIG. 13B, photos of the fabricated stators ofsingle-wound 9-phase VR resolver and balance-wired 9-phase VR resolverare shown, respectively.

In FIG. 14A and FIG. 14B, photos of the fabricated quasi-square waveformrotor lobe (1×) and sinusoidal-waveform rotor lobe (4×) are shown,respectively.

In FIG. 15A and FIG. 15B, photos of the assembled single-wound 9-phaseVR resolver and balance-wired 9-phase VR resolver are shown,respectively.

It is confirmed that the fabricated 9-phase VR resolver generates9-phase amplitude modulated sinusoidal or quasi-square waveformdisplacement signals, depending on the rotor lobe shape installed,without any noticeable distortions. This proves that the newly proposedmulti-phase resolver topology achieves a well-balanced magnetic fluxstate. It is also checked on the scope that the differential synthesismodule implemented by the OP-amp circuitry produces clean two-phaseorthogonal displacement signals.

To measure the orthogonality of the two-phase orthogonal displacementsignals obtained from the fabricated 9-phase VR resolvers, Lissajousgraph is drawn on the oscilloscope in X-Y mode. FIG. 16A shows aquasi-square waveform signal captured on the oscilloscope sensed at theexcitation-sensing coil of the single-wound 9-phase VR resolver when thequasi-square waveform rotor lobe (1×) is installed. It is seen that thecarrier frequency of the signal is 10 kHz and its envelope is aquasi-square (trapezoidal) waveform.

The 9 phase-delayed quasi-square waveform displacement signals areprocessed by the differential synthesis module. FIG. 16B shows aLissajous graph captured on the oscilloscope for the two-phaseorthogonal displacement signals produced by the differential synthesismodule, where it is seen that the orthogonality is held very well andits outline shape is an 18-gon as expected.

FIG. 17A shows an amplitude modulated sinusoidal displacement signalcaptured on the oscilloscope sensed at the excitation-sensing coil ofthe single-wound 9-phase VR resolver when the sinusoidal-waveform rotorlobe (4×) is installed. It is seen that the carrier frequency of thesignal is 10 kHz and its envelope is a sinusoidal waveform having 4electrical periods (4×) per one mechanical turn.

The sensed 9 phase-delayed sinusoidal displacement signals are processedby the differential synthesis module. FIG. 17B shows a Lissajous graphcaptured on the oscilloscope for the two-phase orthogonal displacementsignals produced by the differential synthesis module, where it is alsoseen that the orthogonality is held very well and its outline shape is anear pure circle.

FIG. 18A shows an amplitude modulated sinusoidal displacement signalcaptured on the oscilloscope, sensed at the excitation-sensing coil ofthe balance-wired 9-phase VR resolver when the sinusoidal-waveform rotorlobe (4×) is installed. Compared to the single-wound resolver signal inFIG. 17A, due to it being balance-wired, the amplitude of theun-modulated carrier signal decreases as the flux distribution in thestator has been changed but the sinusoidal envelope of the signal ismore precise than that in FIG. 17A.

The 9 phase-delayed sinusoidal displacement signals are processed by thedifferential synthesis module. FIG. 18B shows a Lissajous graph capturedon the oscilloscope for the two-phase orthogonal displacement signalsproduced by the differential synthesis module, where it is also seenthat its outline shape is closer to a pure-circle than that of thesingle-wound case in FIG. 17B.

The precise displacement position (θ) of the rotor is calculated bytaking the arctangent of two-phase orthogonal displacement signals in acommercially available resolver to digital (R/D) converter or aninterpolator after demodulation.

The test and evaluation results of the fabricated 9-phase VR resolversverify the validity of newly proposed multi-phase resolver topology inproducing N-phase sinusoidal or quasi-square waveform displacementsignals, depending on the rotor lobe shape installed. Also, it isconfirmed that the differential synthesis module realized by thedifferential OP-amp circuitry produces clean two-phase orthogonaldisplacement signals, from which the accurate and precise positioninformation is determined as their Lissajous graph shape is close to apure-circle or 2N-gon.

In the disclosed multi-phase VR resolver, the state of balanced magneticflux distribution is achieved by the topology of the resolver bodyitself, circumventing the extremely complicated coil-winding tasks andsignificantly reducing the rotor lobe's sophisticated design and precisemanufacturing requirements. The prevailing difficulty to achieve preciseand 100% amplitude modulated signals in the conventional VR resolversare also effectively reduced as the under-modulated signals are allowedin multi-phase VR resolver. The signal processing of the differentialsynthesis module optimally converts the multi-phase displacement signalsinto the two-phase orthogonal signals as well, while removing the commonmode noise and component of un-modulated carrier signal if anyun-modulated signal is included.

The newly proposed multi-phase resolver provides a more economic andpractical way to build and manufacture a variety of resolvers that areused in industries while achieving increased flexibility in multi-speedoperation, improved accuracy in position detection, and enhancedreliability in coil insulation.

The claimed subject matter has been described above with reference toone or more features or embodiments. Those skilled in the art willrecognize, however, that changes and modifications may be made to theseembodiments without departing from the scope of the claimed subjectmatter. These and various other adaptations and combinations of theembodiments disclosed are within the scope of the claimed subject matteras defined by the claims and their full scope of equivalents.

What is claimed is:
 1. A multi-phase wound-rotor (WR) resolver apparatusfor measuring a displacement position of a circular movement body, themulti-phase WR resolver apparatus comprising: a stator including: an Nnumber of coil-poles placed at N equally divided positions over amechanical or an electrical period of the stator, N being an odd numbergreater than or equal to 5, wherein the N coils have an identicalelectrical polarity, and are wound with an equal number of windingturns, and the N number of coils sense a displacement of the rotor; anda wound-rotor, wherein a coil is wound with a sinusoidally distributedwinding, a driving signal carrier is applied to the coil wound on thewound-rotor, and one or more periods of sinusoidal electrical signalsare induced on each of the N number of coils on the stator per one turnof the wound-rotor such that N sequentially phase-delayed and amplitudemodulated displacement signals are sensed from the N number of coils onthe stator.
 2. The multi-phase WR resolver apparatus of claim 1, whereineach of the N number of coils is subdivided into two sensing-coils onthe stator, wherein the two sensing-coils are located at 180° differencein mechanical or electrical angle on the stator, wherein the twosensing-coils have an opposite electrical polarity, and are seriallyconnected such that the N number of sequentially phase-delayed andamplitude modulated displacement signals are obtained from N sets of twosubdivided sensing coils.
 3. The multi-phase WR resolver apparatus ofclaim 2, wherein the two sensing-coils are placed at a dual stator on ashared axis, wherein the dual-stator includes a stator-A and a stator-Bon a shared axis, wherein the two sensing-coils are separately placed onthe stator-A and the stator-B at a same electrical angle position, withan opposite electrical polarity, and are serially connected, wherein aphase-delayed displacement signal, free of a common mode noise inducedfrom a directional external magnetic flux toward the resolver, isattained through the two sensing-coils on the dual stator and whereinthe N number of sequentially phase-delayed and amplitude modulateddisplacement signals are obtained from N sets of the two sensing coilson the dual stator.